This worked in Brunei: cut a squash ball in half; cut a slit in it and slide hammock strap through for tight-fitting drip stopper.

I’ve used a couple of old cheap guy lines on strap. I’ve got a daisy chain straps so I just tie a few on each side. Putting one on top and moving down and put the other on the bottom. Just a simple figure 8 knot with the other end feed though it. With that in mind I’ve never been in a major rainstorm. But for a small rain it worked for me. But I do need to get something what’ll work for all types of rainstorms. That way I won’t have to worry about the rain at all.

*water break, not drip lines.

Gotcha. Yeah, that advice is really important in climbing situations, but for small gauge tarp applications, it’s not much of an issue. In my own experience, using line of the same diameter has worked fine. Sheathed line has a better bight, and smaller diameter can be helpful, but because the tension is less than in climbing situations, it doesn’t have the slipping issue. Dyneema line can be more problematic, but I often just use additional wraps and snug it up.

I’m sure the reason for the question is that all directions one finds for tying a prusik specify that the prusik cord be only 1/2 as thick as the main line. For example:

https://www.netknots.com/rope_knots/prusik-knot

I’m not sure I understand your question. Tying a prusik is pretty basic and just loops over the line.